The nuke question is something I'm still undecided on.
As for killing Hitler as a baby, I wouldn't. While WWII was tragic and took the lives of many, the butterfly effect that resulted created as many, if not more. People were dispersed, and they met new people that were found at their new home. In some cases, a refugee married someone they met in their new home, resulting a new bloodline being created. In other cases, someone had a changed outlook on life after the war, which resulted in that someone marrying a different person than they would have previously. Same concept.
To be honest, I don't think I would exist if WWII never happened. My grandfather was in the Navy during WWII, stationed in the Pacific theater. He never saw battle, but I would be shocked if his experience in the military didn't change him. It certainly impacted his decisions going forward, which likely ensured he would meet and eventually marry my grandmother.
I can guarantee I'm not the only one who wouldn't exist if WWII didn't happen. Should I sacrifice myself, many of the people I know, and who knows how many others around the world, for the sake of those whose fate was already decided back then? Absolutely not.
Sure, there'd be many individuals that would exist in place of us all; however, they don't exist, so we have no moral obligation to them. We have the people in this world right now.
And that's not even factoring in the future, where the butterfly effect would get even more intense.